The role of fire in atmospheric chemistry Discussion with
Susquehanna University Green Chemistry class Sonia Kreidenweis
Colorado State University
Slide 2
Worldwide occurrence of fire
Slide 3
Mean annual fire emissions, 1997-2004 (g C m -2 year -1 ) (van
der Werf et al., ACP, 2006) Which locations are mostly WILDFIRES?
Which are PRESCRIBED fires? Why do people use prescribed
burning?
Slide 4
Burning in North America (Image: from van der Werf et al., ACP,
2006) In the U.S., about 2 million acres per year of federal
forests were burned by prescribed fires from 1998 to 2006, in
comparison to around 6 million acres of wildfires (Tian et al.,
ES&T, 2008) Which are prescribed burning?
Slide 5
In a typical year, how much of the CARBONACEOUS particulate
matter in the US can be attributed to fire? About 1% About 10%
About 50%
Slide 6
Biomass burning can contribute ~50% of annual mean carbonaceous
aerosol in U.S.
Slide 7
Sugar cane burn, LA
Slide 8
Prescribed fire in Georgia Joseph W. Jones Ecological Research
Center wiregrass and longleaf pine needles and underbrush
Slide 9
Lightning-started peat fire Firefighters battle burning peat at
Pocosin Lakes National Wildlife Refuge in North Carolina, January
2009. USFWS, posted at
http://www.cbsnews.com/8301-501465_162-20024255-501465.html Typical
of swampy areas, peat soils consisting of organic matter burned and
held intense heat. Soaking the peat with water was the only way to
fully extinguish the underground fire. (reported at
http://www.fws.gov/fire/news/nc/ev ans_road.shtml)
Slide 10
Chaparral Chaparral canyon fire near Rancho Peasquitas (1995)
Reported by The San Diego Wildfires Education Project,
http://interwork.sdsu.edu/fire/resources/chapparal-charecteristics.htm
Slide 11
Alaska boreal forest wildfire
Slide 12
How far does a smoke plume travel? About 50 km About 100 km
Several hundred km Question is not worded properly
Slide 13
NOAA Smoke Forecasting
Slide 14
Aerosol optical depth in Boulder summer 2012 AP Photo/Ed
Andrieski
Slide 15
True or false? The mix of emitted species changes from the
beginning to the end of a fire. Most of the mass of burned biofuels
is emitted as particles. Fires always emit a lot of black carbon
(soot). A fire will always result in a high-ozone episode in the
nearby areas affected. The particles that are emitted might
evaporate as the smoke plume is diluted.
Slide 16
Composition of emissions from biomass burning (where does the
carbon in the plant go?) Andreae & Merlet, Global
Biogeochemical Cycles, 2001 carbon dioxide (CO 2 ) [92 96 %] carbon
monoxide (CO) [3 7 %] everything else [ < 2 %]
Slide 17
Whats in the everything else? Andreae & Merlet, Global
Biogeochemical Cycles, 2001 methane (CH 4 ) [10 30 %] non-methane
hydrocarbons [20 40 %] particulate matter [ > 30 %]
Slide 18
Yokelson et al., J. Geophys. Res., 1996 Where does N in the
plants go?
Slide 19
Pyrolysis Pyrolysis is a thermochemical decomposition of
organic material at elevated temperatures in the absence of oxygen
(or any halogen). It involves the simultaneous change of chemical
composition and physical phase, and is irreversible. The word is
coined from the Greek-derived elements pyro "fire" and lysis
"separating".thermochemical decompositionorganic material
oxygenhalogenchemical composition Greekelementslysis Pyrolysis is a
type of thermolysis, and is most commonly observed in organic
materials exposed to high temperatures. It is one of the processes
involved in charring wood, starting at 200300 C (390570 F)
[Wikipedia]thermolysisorganiccharring
Slide 20
Conceptual picture new particle formation
Slide 21
Conceptual picture new particle formation OZONE FORMATION
Slide 22
Direct evidence for health impacts of smoke
Slide 23
Study Finds Peat Wildfire Smoke Linked to Heart Failure Risk In
the summer of 2008, a lightning strike started a wildfire in
eastern North Carolina that burned for weeks, blanketing nearby
communities in smoke. An EPA study shows for the first time that
smoke from this wildfire, which was fueled by peat (decayed
vegetable matter found in swampy areas) can lead to an increase in
emergency room visits for both respiratory and cardiovascular
effects. This was the first study to report increased visits for
symptoms of heart failure in counties exposed to wildfire smoke.
The study found a 37 percent increase in emergency room visits for
people with symptoms of heart failure during a three day period of
dense smoke exposure and the following five days. The EPA study
also showed an increase in emergency department visits for problems
relating to asthma, chronic obstructive pulmonary disease (COPD),
pneumonia, and bronchitis, which are similar to studies of other
wildfires. http://www.epa.gov/research/htm/wildfire.htm
Slide 24
Ozone also rises when plumes arrive Air pollutants from a
prescribed fire about 80 km southeast of metro Atlanta on February
28, 2007 led to parts of the city being exposed to unhealthy levels
of PM 2.5 for several hours. Observed 1-h PM 2.5 concentrations at
several monitors in the city reached higher than 145 g/m3 (U.S.
National Ambient Air Quality Standard (NAAQS) for 24-h PM2.5 is 35
g/m3), increasing by over 100 g/m3 in two hours. In addition, as
the plume hit, 1-h average ozone concentrations increased markedly
from 63 to 95 ppb at one monitor. Tian et al., ES&T, 2008
Slide 25
Air Quality Impacts
Slide 26
National Ambient Air Quality Standards: smoke impacts? Fire
influence is UNDER DEBATE (fire probably leads to increased ozone
downwind)
Slide 27
National Ambient Air Quality Standards: smoke impacts? No
direct impact, but together with other emitted gases, can lead to
high ozone levels
Slide 28
National Ambient Air Quality Standards: smoke impacts? Very
important, not only locally but over large regions! Standards are
being lowered in response to health data.
Slide 29
Strategies for the future? Wildland fire is a complicated
subject when considered under the Regional Haze Rule (RHR). While
prescribed fire emits pollutants which contribute to haze, a series
of prescribed fires may emit less pollutants than one wildfire.
http://www.frames.gov/partner-sites/emissions-and-
smoke/educational-resources/tutorial/lesson-2/regional-haze/